128 STRUCTURE AND CLASSIFICATION OF BIRDS 



the name ratite (raft-like), or at most, as in Eliea, a slight 

 protuberance, which, however, as will be pointed out imme- 

 diately, is not really comparable to the keel of the carinate 

 birds. There are, however, other birds, such as the extinct 

 Cnemiornis and the living 

 Stringops, in which the 

 keel is absent, its ab- 

 sence being associated 

 with the loss of the 



ts.OC 



m.x 



FIG. 72 STERNUM OF Loplio- 

 pliorus impeyanus (AFTER HUXLEY). 



x, rostrum ; cj>, anterior lateral process ; 

 ji.t.n, posterior lateral process ; e..i; /'../, 

 its inner and outer divisions ; l.o. cariua. 



FIG. 73. STERNUM OF Podica 

 senegalensis (AFTEK BEDDABD). 



cl, clavicle ; co, - coracoid ; cl, x, articula- 

 tion of clavicle. 



power of flight. In the singular Opistliocomus the anterior 

 part of the keel is, as it were, cut away (the enormous crop 

 resting here), the posterior region being retained. The four 

 posterior lateral processes of the sternum figured above are 

 not always present in birds. The extremest modification 

 is as seen in the goose and the crane, where the posterior 



